Fulham-based Aryn Stones Ltd was conducting remedial work at a house in Hampstead when the incident occurred on May 31, 2022.
Two workers, a 62-year-old welder and a 31-year-old bricklayer, suffered life-changing injuries when the partially built beam-and-block floor gave way.
Two other men, standing at ground level, were injured by falling concrete.
The structure’s collapse was a result of identified flaws in the connections of the structural steel beams, found during an inspection in February 2022.
The collapse happened during work to remedy this.
As one welder used an oxyacetylene torch to cut a steel beam supporting the first floor, another worker was simultaneously removing Acrow props providing additional support.
This led to the floor’s collapse.
The Health and Safety Executive (HSE) investigation revealed that Aryn Stones Ltd had failed to ensure the structure did not collapse while it was in a state of temporary weakness.
The company also neglected to implement measures to manage the temporary remedial work on the steel connections and did not take all practicable steps to prevent danger to any person while the building was in a temporary state of weakness.
The company’s negligence resulted in a breach of the Construction (Design and Management) Regulations 2015.
After a two-day trial before the City of London Magistrates’ Court on June 18, 2025, the company was handed a £50,000 fine and ordered to pay £39,000 in costs.
After the hearing, HSE inspector Lucy Ellison-Dunn said: “Although two men were seriously injured, it was lucky nobody was killed.
“This was a completely avoidable incident had a system for the management of temporary works been in place.
“The company should have taken precautions to protect people from the risk of collapse.
“Everyone working in construction has a responsibility to ensure that everyone on a building site is safe.”
The investigation was also carried out by HSE inspector Alexander McIlwraith.
The prosecution was brought by HSE enforcement lawyer Samantha Crockett and supported by HSE Paralegal Officer Sarah Thomas.
